A lot of people have different rules of thumb for radiator space, but all will agree what you have is not enough to manage what's in it. Like someone else said the tube routing is terrible, and it probably wasting a good deal of flow rate from the pump as a result of excess tubing, which may worsen your temps. Given whoever made this clearly wasn't doing a lot of research when they did it, I'd also wonder how well they mounted the GPU block, and how well they seated the CPU block. My personal rule of thumb for radiators is every 120mm worth of rad space will provide around 100W of dissipation with decent fans at a decent temperature. The 920 is 130W tdp plus maybe an extra 30-50% for an overclock, and the GPU is 182W, maybe an extra 30% for overclocking headroom, you're looking at around 300-350 watts ish min. Like someone said earlier a 360mm (3x120mm) rad or even a 420mm (3x140mm) rad would probably be what I'd want to use for something like that.

As for fans the GTs are great, but slightly pricey. I personally recommend the Cougar Vortex fans. They're relatively cheap (around 14 bucks) and perform on par with Noctuas (a little bit louder, but a little bit cooler too) and are great quality. Other options include corsair SP120s and noctuasEdited by PhantomTaco - 4/3/13 at 1:34pm

I'd probably start by changing that 120mm rad to a 240mm with fans in a push pull configuration (4 fans). On top of that, i'd set the gpu to be second in the loop personally. The cpu runs hotter, because your gpu is heating the water before it makes it into the cpu. Both of those components (gtx260 and i7 920) run quite hot. Dont expect much above 3.5ish ghz on even the 240mm rad configuration.

I'd probably start by changing that 120mm rad to a 240mm with fans in a push pull configuration (4 fans). On top of that, i'd set the gpu to be second in the loop personally. The cpu runs hotter, because your gpu is heating the water before it makes it into the cpu. Both of those components (gtx260 and i7 920) run quite hot. Dont expect much above 3.5ish ghz on even the 240mm rad configuration.

I'm not going for a seriously high OC, I'm thinking a modest one, kind of like a 4.4 GHz OC on a 2600k or 3570k.

I have another quick question: What is a reasonable temperature for a 920 to idle at in Windows? I've been reading that with a Hyper 212, 45C is reasonable, but I find that a bit high. Can someone give me a rough estimate of what it should be at idling with a water cooling loop with a 240MM rad with just the CPU in the loop?

In a few minutes here I'm going to unplug the GPU from the system, so it isn't generating heat, and see what kind of temps I get with just the CPU in the loop (and water flowing over the unplugged GPU).

EDIT: I started the PC up this morning from sleep mode, and the idle temps for around 5 minutes or so were 30-28-28-29, which I think is fairly good. I started a Prime95 run then, and now the max temps on the cores are 72-72-67-74, which is still pretty high. At least the idle temperatures are alright.

EDIT 2: After stopping the Prime95 test, now the idle temps on max fan speed after 3 minutes or so are 44-43-42-44, not sure what's going on.

EDIT: I started the PC up this morning from sleep mode, and the idle temps for around 5 minutes or so were 30-28-28-29, which I think is fairly good. I started a Prime95 run then, and now the max temps on the cores are 72-72-67-74, which is still pretty high. At least the idle temperatures are alright.

EDIT 2: After stopping the Prime95 test, now the idle temps on max fan speed after 3 minutes or so are 44-43-42-44, not sure what's going on.

That would be indicative that there isn't enough radiator to cool down the water fast enough once it got hot, which would explain why even after 5 minutes after stopping, the water is still hot. Adding more radiator capacity will allow the heat to be transfered from the water to the air and then blown away by the fans. With too little radiator, the transfer of heat from water to air can not take place fast enough and the heat just remains trapped in the water for a long time.

That would be indicative that there isn't enough radiator to cool down the water fast enough once it got hot, which would explain why even after 5 minutes after stopping, the water is still hot. Adding more radiator capacity will allow the heat to be transfered from the water to the air and then blown away by the fans.

Hmmm, so then that leads me to believe that the thermal paste was put on correctly, if I saw temps of around 30C before.

Thanks for all the help everyone, except I can't test the system without a GPU. Blasted motherboard has two ethernet ports, but no onboard video. How does that even make sense?